Process for preparing a hydrotreating catalyst

ABSTRACT

Process for preparing a hydrotreating catalyst comprising of from 5 wt % to 50 wt % of molybdenum, of from 0.5 wt % to 20 wt % of nickel and of from 0 to 5 wt % of phosphorus, all based on total dry weight of catalyst, which process comprises (a) treating alumina carrier with molybdenum and nickel and of from 1 to 60% wt of gluconic acid, based on weight of carrier, and op tionally phosphorus, (b) optionally drying the treated carrier at a temperature of from 40 to 200° C., and (c) calcining the treated and optionally dried carrier at a temperature of from 200 to 650° C. to obtain the calcined treated carrier.

FIELD OF THE INVENTION

The present invention relates to a process for preparing hydrotreatingcatalyst.

BACKGROUND OF THE INVENTION

In the catalytic hydroprocessing of hydrocarbon feedstocks, such ascrude oil, distillates and residual crude oil fractions, catalystcompositions containing hydrogenation metals are used to promotedesulfurization and denitrogenation reactions and thereby provide forthe removal of organic sulfur and organic nitrogen compounds from thehydrocarbon feedstocks. The processes involve contacting catalystparticles with a hydrocarbon feedstock under conditions of elevatedtemperature and pressure and in the presence of hydrogen to convertsulfur components of the feedstock to hydrogen sulfide and nitrogencomponents of the feedstock to ammonia. The hydrogen sulfide and ammoniasubsequently are removed to give the hydrotreated product.

Hydrotreating catalysts comprise hydrogenation metal components on arefractory oxide. The hydrogenation metal components are generally GroupVI metal components such as molybdenum and/or tungsten and Group VIIImetal components such as nickel and/or cobalt. The porous refractoryoxide support material can typically be alumina. Promoters such asphosphorus may also be used as a component of the hydroprocessingcatalyst.

There is a continuous interest in further improving the performance ofthese catalysts.

A method which can lead to improved performance is treating a carrierwith a solution containing catalytically active metal and an organicligand and subsequently drying the treated carrier. By not calciningsuch dried catalyst, an improved performance can be attained asmentioned in publications such as EP-A-0482818, WO-A-96/41848, WO2009/020913 and WO 2012/021389. The preparation of catalysts which areonly dried but not calcined is relatively complex and cumbersome inactual commercial practice.

The aim of the present invention is to find a process which isrelatively easy to apply while providing a hydrotreating catalyst havinggood activity in the manufacture of low sulphur and nitrogen fuels suchas ultra low sulphur diesels.

SUMMARY OF THE INVENTION

It has now been found that this aim can be attained by treating acarrier with a metal containing impregnation solution further containinggluconic acid.

Accordingly, the present invention relates to a process for preparinghydrotreating catalyst comprising of from 5 wt % to 50 wt % ofmolybdenum, of from 0.5 wt % to 20 wt % of nickel and of from 0 to 5 wt% of phosphorus, all based on total dry weight of catalyst, whichprocess comprises

-   (a) treating alumina carrier with molybdenum, nickel and of from 1    to 60% wt of gluconic acid, based on weight of carrier, and    optionally phosphorus,-   (b) optionally drying the treated carrier at a temperature of from    40 to 200° C., and-   (c) calcining the treated and optionally dried carrier at a    temperature of from 200 to 650° C. to obtain the calcined treated    carrier.

In accordance with the present process hydrotreating catalysts can beprepared with the help of a relatively simple process involving alimited number of process steps. Besides the easy manufacture, theinvention has the advantage that the catalysts obtained were found tohave a high activity in hydrodesulphurization.

DETAILED DESCRIPTION OF THE INVENTION

The catalyst of the present invention is prepared with the help of analumina carrier. Preferably, the carrier consists of alumina. Morepreferably, the carrier consists of gamma alumina.

The porous catalyst carrier may have an average pore diameter in therange of from 5 to 35 nm, measured according to test ASTM D-4222. Thetotal pore volume of the porous refractory oxide is preferably in therange of from 0.2 to 2 ml/gram.

The surface area of the porous refractory oxide, as measured by theB.E.T. method, generally exceeds 100 m²/gram, and it is typically in therange of from 100 to 400 m²/gram. The surface area is to be measured bythe B.E.T. method according to ASTM test D3663-03.

The catalyst contains catalytically active metals on the carrier. Thesecatalytically active metals are molybdenum in combination with nickel.It is preferred that additionally phosphorus is present. Therefore, thetreated alumina carrier preferably consists of molybdenum, phosphorus,gluconic acid and nickel.

The metal component can be the metal per se or any component containingthe metal, including but not limited to metal oxides, metal hydroxides,metal carbonates and metal salts.

For nickel, the metal component preferably is chosen from the groupconsisting of acetates, formates, citrates, oxides, hydroxides,carbonates, nitrates, sulfates, and two or more thereof. Preferably, thenickel component is a metal nitrate.

For molybdenum, preferred metals salts are molybdenum oxides andmolybdenum sulphides. More preferred are salts additionally containingammonium, such as ammonium heptamolybdate and ammonium dimolybdate.

The phosphorus compound that is used preferably is chosen from the groupconsisting of acids of phosphorus, such as metaphosphoric acid,pyrophosphoric acid, orthophosphoric acid and phosphorous acid, andprecursors of an acid of phosphorus. The precursor is aphosphorus-containing compound capable of forming at least one acidichydrogen atom in the presence of water. Preferred precursors arephosphorus oxide and phosphorus. The preferred acid of phosphorus isorthophosphoric acid (H3PO4).

The nickel can be present in the hydrotreating catalyst in an amount inthe range of from 0.5 wt % to 20 wt %, preferably from 1 wt % to 15 wt%, and, most preferably, from 2 wt % to 12 wt %, based on metal on totaldry weight of the hydrotreating catalyst.

The molybdenum can be present in the hydrotreating catalyst in an amountin the range of from 5 wt % to 50 wt %, preferably from 8 wt % to 40 wt%, and, most preferably, from 10 wt % to 30 wt %, based on metal ontotal dry weight of catalyst. Most preferably, the amount of molybdenumis at least 11% wt, more specifically at least 12% wt, more specificallyat least 13% wt, most specifically at least 14% wt.

The phosphorus preferably is present in the hydrotreating catalyst in anamount in the range of from 0.1 to 5 wt %, preferably from 0.2 wt % to 5wt %, and, more preferably, from 0.5 to 4.5 wt %, based on phosphorus ontotal dry weight of catalyst. Most preferably, the amount of phosphorusis of from 1.5 to 3.5% wt, based on total dry weight of catalyst.

The metals generally will be present in the form of an oxide or sulfide.For determining the metal content, it is assumed that they are presentin the form of the metal per se independent of their actual form orstate. The dry weight is the weight assuming that all volatile compoundssuch as water and gluconic acid have been removed. The dry weight can bedetermined by keeping the catalyst at a temperature of 400° C. for atleast 2 hours. For the calculation of phosphorus content, phosphorus isassumed to be present as the element independent of its actual form.

The amount of gluconic acid preferably is of from 2 to 40% wt ofgluconic acid, based on weight of dry carrier, more preferably of from 3to 30% wt, more specifically of from 4 to 20% wt.

Preferably, the hydrotreating catalyst consists of from 0.5 wt % to 20wt % of nickel, of from 5 wt % to 50 wt % of molybdenum and of from 0.1to 5 wt % of phosphorus, all metal based on total dry weight ofcatalyst, on an alumina carrier, more preferably a carrier consisting ofgamma alumina.

The catalytically active metals, gluconic acid and phosphorus preferablyare incorporated in the carrier by treating the carrier with a solutioncontaining these components. Most preferably, the components are addedby pore volume impregnation with the help of a solution containing thesecomponents. It is preferred that all components are present in a singlesolution, most preferably an aqueous solution. It can be that not allcomponents can be combined in a single impregnating solution for examplebecause of stability problems. In such instance, it can be preferred touse two or more solutions with optionally a drying step in between.

The present invention involves treating the carrier with gluconic acid.This can be either gluconic acid or a salt of gluconic acid or an esterof gluconic acid which ester forms gluconate in the solution. If asolution is used for treating the carrier, the solution generally willcontain a salt of gluconic acid possibly besides gluconic acid per se.For the present invention, treating the carrier with a salt of gluconicacid also is considered to be treating the carrier with gluconic acid.Preferably, the solution for treating the carrier is prepared by addinggluconic acid to the solvent.

Preferably, the ratio of weight amount of gluconic acid to the totalweight amount of nickel and molybdenum deposited on the carrier is offrom 0.1 to 5, more specifically of from 0.1 to 3, more specifically offrom 0.2 to 3, more preferably of from 0.3 to 2.5, more preferably offrom 0.5 to 2, more preferably of from 0.6 to 1.8, most preferably offrom 0.7 to 1.5.

In step (b) the treated carrier can be dried before the calcination ofstep (c). Whether drying indeed should be carried out and if so, underwhat conditions, depends on the amount of volatile components presentand on the subsequent calcination conditions. Generally, drying will becarried out during of from 0.1 to 6 hours at a temperature of from 40 to200° C., more specifically during of from 0.5 to 4 hours at atemperature of from 100 to 200° C. Most preferably, drying is carriedout by indirect heating which means that the environment surrounding thecomposition is heated. Indirect heating excludes the use of microwaves.

The calcination of step (c) preferably is carried out during of from 0.1to 6 hours at a temperature of from 200 to 650° C., more specificallyduring of from 0.5 to 4 hours at a temperature of from 250 to 600° C.,more specifically of from 280 to 550° C.

Without wishing to be bound to any theory, it is believed that theimproved performance is due to the interaction between catalyticallyactive metal, carrier and gluconic acid. It is believed that theinteraction leads to smaller metal oxide particles upon calcinationwhich smaller particle size is maintained during sulphidation.

The calcined treated carrier preferably is sulphided before being usedin hydrotreating. Therefore, the process of the present inventionpreferably further comprises (d) sulphiding the calcined treated carrierto obtain the hydrotreating catalyst.

After sulphidation, which can be carried out in-situ or ex-situ, thecatalyst is considered to be ready for commercial use.

The present invention also provides a process for hydrotreating asulphur-containing hydrocarbon feedstock which process comprisescontacting the hydrocarbon feedstock at a hydrogen partial pressure from1 to 70 bar and a temperature of from 200 to 420° C. with a catalystobtained in accordance with the present invention.

Sulphidation of the calcined treated carrier can be done using anyconventional method known to those skilled in the art. Thus, thecalcined treated carrier can be contacted with a gaseous streamcontaining hydrogen sulphide and hydrogen. In another embodiment, thecalcined treated carrier is contacted with a sulphur-containing compoundwhich is decomposable into hydrogen sulphide, under the contactingconditions of the invention. Examples of such decomposable compoundsinclude mercaptans, CS₂, thiophenes, dimethyl sulfide (DMS), anddimethyl disulphide (DMDS). A further and preferred option is toaccomplish sulphidation by contacting the composition, under suitablesulphurization treatment conditions with a hydrocarbon feedstock thatcontains a sulphur-containing compound. The sulphur-containing compoundof the hydrocarbon feedstock can be an organic sulphur compound,particularly, one which is typically contained in petroleum distillatesthat are processed by hydrodesulphurization methods. Typically, thesulphiding temperature is in the range of from 150 to 450° C.,preferably, from 175 to 425° C., and, most preferably, from 200 to 400°C.

The sulphiding pressure can be in the range of from 1 bar to 70 bar,preferably, from 1.5 bar to 55 bar, and, most preferably, from 2 bar to45 bar.

The present invention is explained in more detail in the followingexamples.

EXAMPLES Example 1 Nickel/molybdenum Containing Catalyst

Commercial carrier was prepared by extruding pseudo-boehmite into 1.3 mmtrilobes and drying and calcining these to provide alumina carrier asdescribed in Table 1.

The average pore diameter was measured according to ASTM test D-4222.The surface area was measured according to ASTM test D-366303.

TABLE 1 Alumina carrier properties Property Carrier Calcination 535temperature (° C. ) BET Surface Area 300 (m²/g) Average Pore  9 Diameter(nm)

The metal components of the catalyst were incorporated into the abovecarrier by pore volume impregnation to yield the following metalscomposition (weight of metal based on dry weight of total catalyst): 15%Mo, 3.5% Ni, 2.2% P. The impregnation solution included phosphoric acid,nickel oxide, molybdenum trioxide and gluconic acid. The total volume ofthe resulting solution was equal to 98% of the water pore volume of thealumina carrier. The gluconic acid concentration in the impregnationsolution was 20% wt corresponding with a gluconic acid content of 12.5%wt based on carrier.

The impregnated carrier was then dried at 110° C. for 2 hours andsubsequently calcined for 2 hours at 400° C. to remove gluconic acid.

The following catalyst was obtained.

TABLE 2 Ni/Mo catalyst Amount of Compacted gluconic bulk acid (% wtCalcination density Catalyst on carrier) temperature (g/ml) 1 12.5 4000.72

Example 2 Catalyst Activities

Trickle flow micro-reactors were used to test the desulfurizationactivity of the catalyst according to the invention compared with acommercial reference catalyst.

The compositions were conditioned and sulphided by contacting them witha liquid hydrocarbon containing sulfur spiking agent to provide a sulfurcontent of 2.5% wt. The process conditions used in these tests comprisea gas to oil ratio of 300 Nl/kg, a pressure of 40 bar and a liquidhourly space velocity of 1 h⁻¹. The weight average bed temperature(WABT) was adjusted to a temperature in the range of 340 to 380° C.

The feed used in the tests is a full range gas oil containing 1.28% wtof sulphur.

The process conditions and feed properties are representative of typicalultra-low sulfur diesel (ULSD) operations.

Rate constants were determined assuming a reaction order of 1.25. Thetemperature required to obtain a product containing 10 ppm of sulphur isgiven in Table 3. The lower temperature required to achieve this sulphurcontent and the higher RVA show that the catalysts according to thepresent invention have improved performance.

The relative volumetric activity (RVA) for catalyst 1 was determinedrelative to comparative commercial catalyst containing similar amountsof nickel, molybdenum and phosphorus and having a compact bulk densityof 0.74 ml/g, hereinafter referred to as Comparative Catalyst.

Table 4 shows the temperature required to obtain a product containing 10ppm of sulphur. The lower temperature required to achieve this sulphurcontent and the higher RVA show that the catalyst according to thepresent invention has improved performance over the ComparativeCatalyst.

TABLE 4 Hydrodesulphurization activity Temperature required RVA for 10ppm S (° C. ) (%) Comparative 368.5 100 Catalyst 1 363.9 115

1. A process for preparing a hydrotreating catalyst comprising of from 5wt % to 50 wt % of molybdenum, of from 0.5 wt % to 20 wt % of nickel,and of from 0 to 5 wt % of phosphorus, all based on total dry weight ofcatalyst, which process comprises (a) treating an alumina carrier withmolybdenum and nickel and of from 1 to 60% wt of gluconic acid, based onweight of carrier, and optionally phosphorus; (b) optionally drying thetreated carrier at a temperature of from 40 to 200° C; and (c) calciningthe treated and optionally dried carrier at a temperature of from 200 to650° C. to obtain the calcined treated carrier.
 2. A process accordingto claim 1, in which process the amount of gluconic acid is of from 2 to40% wt, based on total dry weight of carrier.
 3. A process according toclaim 1, in which the amount of phosphorus is of from 1.5 to 3.5% wt,based on total dry weight of catalyst.
 4. A process according to claim1, in which the hydrotreating catalyst consists of an alumina carrierand from 1 wt % to 15 wt % of nickel, of from 8 wt % to 40 wt % ofmolybdenum and of from 0.1 to 5 wt % of phosphorus, all metal based ontotal dry weight of catalyst.
 5. A process according to claim 4, inwhich the carrier is gamma alumina
 6. A process according to claim 1, inwhich the ratio of weight of gluconic acid to the total weight of nickeland molybdenum deposited on the carrier before calcination is of from0.1 to
 5. 7. A process according to claim 1 which process furthercomprises (d) sulphiding the calcined treated carrier to obtain thehydrotreating catalyst.
 8. A process for hydrotreating asulphur-containing hydrocarbon feedstock which process comprisescontacting the hydrocarbon feedstock at a hydrogen partial pressure from1 to 70 bar and a temperature of from 200 to 420° C. with a catalystobtained according to claim 7.